'''练习1：定义一个类描述数字时钟'''
from time import sleep

class Clock(object):
    def __init__(self,hour=0,minute=0,second=0):
        self._hour=hour;
        self._minute=minute;
        self._second=second;

    def run(self):
        '''走表'''
        self._second+=1
        if self._second==60:
            self._second=0;
            self._minute+=1;
            if self._minute==60:
                self._minute=0;
                self._hour+=1;
                if self._hour==24:
                    self._hour=0;

    def show(self):
        return '%0.2d:%0.2d:%02d'%(self._hour,self._minute,self._second)
def main():
    clock=Clock(23,59,58)
    while True:
        print(clock.show())
        sleep(1)
        clock.run()
if __name__ == '__main__':
    main()